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Abstract
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Context: Fatal pedestrian collisions are over-represented at night, with nearly two-thirds of all fatal pedestrian collisions occurring at night-time. Although multiple factors contribute to the increased fatality rate at night, insufficient conspicuity is believed to be a leading cause of collisions with pedestrians, cyclists, and other low-contrast obstacles.
Objectives: The objectives of this research were to better understand how drivers‘ ability to see pedestrians at night is affected by experimentally induced visual impairments (blur and simulated cataracts), and the presence or absence of headlamp glare. In addition, we sought to determine whether clothing configurations that have been shown to improve pedestrian conspicuity are more robust to the effects of visual impairment than other clothing configurations.
Design and Setting: In this research innovative measuring techniques were used on a closed road circuit that mirrors "real world" road conditions. The impact of a range of factors including simulated visual impairment, the presence or absence of glare and different clothing configurations on pedestrian recognition were examined using an instrumented vehicle incorporating a novel parallax-based measuring video system.
Participants: Twenty eight young, visually normal drivers who passed the visual requirements for driving.
Main Outcome Measures: Using a mixed experimental design we recorded how a driver‘s vision, headlamp glare and pedestrian clothing affected the ability of drivers to recognize pedestrians. The distances at which pedestrian recognition first occurred were also recorded.
Results: Visual impairment, headlamp glare and pedestrian clothing all significantly affected drivers' ability to respond to pedestrians (p<0.05). Although simulated cataracts and blur each resulted in significantly degraded recognition performance, the simulated cataracts were more disruptive than the blur manipulation, even though visual acuity was matched across conditions. The presence of headlamp glare also reduced pedestrian conspicuity. Pedestrians were recognized more often and at longer distances when they wore "biomotion" clothing than either the reflective vest or black clothing, even in the presence of visual impairment and glare.
Conclusions: These findings indicate that drivers‘ ability to see and respond to the presence of pedestrians at night is degraded by common visual impairments even when the impairments did not degrade visual acuity below the standards that are typically used to determine visual licensing requirements. Headlamp glare further exacerbated the mild visual impairments. Clothing configurations that include retroreflective tape in a biological motion configuration are relatively robust to the effects of visual impairment and glare. |